As an example of an image recording apparatus, related art discloses an inkjet recording apparatus configured to record an image by repetitively performing a scanning operation (recording pass) of discharging ink from a plurality of nozzles while moving a carriage, on which a recording head having the nozzles is mounted, in a scanning direction, and a sheet conveying operation. In the inkjet recording apparatus, there is a problem that a stripe-shaped density irregularity (for example, a white stripe) is generated in the scanning direction on a sheet due to a conveyance error. As measures against the stripe-shaped density irregularity, the related art discloses an image recording by a multi-pass recording method of completing an image of one line to be recorded on the sheet in the scanning direction by recording a thinned-out image by using different nozzles in each of a plurality of recording passes.
As the image recording apparatus of the above type, an image recording apparatus has been suggested which is configured to execute unidirectional recording, in which the recording pass is performed by discharging the ink from the nozzles only when the carriage is moved toward one side in the scanning direction, and bidirectional recording, in which the recording pass is performed by discharging the ink from the nozzles when the carriage is moved toward one side and another side in the scanning direction. In the unidirectional recording, a quality of an image to be recorded on a sheet is higher but the throughput is lowered, as compared to the bidirectional recording.
Also, the stripe-shaped density irregularity in the scanning direction may be generated due to diverse factors, in addition to the conveyance error. For example, in a case where a nozzle shift (bending of a flight course of the discharged ink droplets) occurs, the stripe-shaped density irregularity in the scanning direction may be generated. As measures against the stripe-shaped density irregularity due to the nozzle shift, it is useful to record an image by the multi-pass recording method as described above. Also, in a case where an amount of the nozzle shift is large, it is possible to further diminish the stripe-shaped density irregularity by increasing the number of times of the recording passes upon recording of an image of one line. However, when the number of times of the recording passes is increased, the throughput is lowered. Therefore, for example, when an image is recorded on the sheet by the unidirectional recording and the number of times of the recording passes upon recording of an image of one line is increased, the throughput may be largely lowered.